Semantic networks are a well-known knowledge representation mechanism. A semantic network includes nodes representing concepts, objects, actions (these are referred to hereafter as concept nodes or simply nodes), connected by directional links defining the relationships between nodes (See. e.g., Quillian, M. R. (1968). Semantic memory, In M. Minsky (Ed.), Semantic Information Processing (pp. 227-270). Cambridge, Mass.: MIT Press). Semantic networks can be, and often are, represented visually/graphically.
When semantic networks are graphically depicted, they are also known as concept maps (See, e.g., Kommers, P. A. M., Jonassen, D. H. & Mayes, J. T. (Eds.) (1992). Cognitive Technologies for Learning. Berlin: Springer-Verlag). Hence, a concept map is a visual representation of knowledge of a domain. Concept maps have also been called knowledge maps, semantic maps, webs, and semantic webs (See, Bromley, K. D. (1996). Webbing with Literature: Creating Story Maps with Children's Books (Second Edition). Needham Heights, Mass.: Allyn & Bacon). Concept maps are often drawn with a computer-based editor, so as to share knowledge among people.
Visually, a node may be represented by a geometric object, for example a rectangle or oval, containing a textual label or name. Each relationship link is represented by a line with an arrowhead at one or both ends. In some concept mapping tools, links may also be textually labeled. Together, nodes and labeled links define propositions, which may include assertions about a topic, domain, or thing. FIG. 1 is an example of a concept map where the nodes and link represent the knowledge “birds have wings”.
A small number of concept map tools automate the conversion of concept maps to outlines. Many users of concept map tools may also wish to see their ideas/thoughts/knowledge organized in outline form. However, the few existing tools that do such translation elide from the outline much of the important knowledge and information that is contained in the concept map.
Concept mapping tools that include the ability to translate a concept map to outline format include Learning Tool (See Kozma, R. B. (1992). Constructing knowledge with Learning Tool, in P. A. M. Kommers, D. H. Jonassen, and J. T. Mayes (Eds.), Cognitive Technologies for Learning (pp. 23-32). Berlin: Springer-Verlag) and INSPIRATION® (Inspiration Software, Inc. (1998). Classroom Ideas Using Inspiration®: For Teachers by Teachers. Portland, Oreg.: Inspiration). The most prominent and representative example of prior art is the INSPIRATION® software product. Inspiration is a popular consumer product for computer-based concept mapping. The INSPIRATION® product can produce outlines from concept maps, but there are significant problems with these outlines and these problems are evident in the other concept map tools as well.
First, labels that appear on inter-node links are ignored in Inspiration's outlines; these labels appear nowhere in the outline translation of a map. The labels on links provide a primary source of knowledge in a concept map, the labels define the relationships between two nodes, and without labels on inter-node links, all that is known from the map is that there is some relationship between the connected nodes.
The problem in eliding the labels on inter-node links from the outline translation of a concept map is that because these concept-to-concept relationships provide important semantic information the outline is an impoverished representation of the knowledge contained in the map. If a user believed it important to name the relationship between two concepts, this information ought to be incorporated into the alternative outline representation of that user's concept map.
So, for example, for the concept map shown in FIG. 2a, if the link labels were disregarded in FIG. 2a and only concept nodes were included, a portion of the outline view may appear as:
animal                I. skin        II. oxygen        . . .However, this is a rather anemic translation of the information contained in the map, eliding much of the semantic information in the map which is provided by the link labels.        
Second, concept maps may have multiple layers of knowledge and information. In INSPIPATION's® translation of a concept map to an outline, only the information in a single level of the map is included in an outline. That is, none of the knowledge or information in any of the child/sub-maps is included. A user may request an outline translation of each sub-map individually. Not only is this cumbersome, but the entire set of knowledge elements, that is, the entirety of the knowledge represented by the overall concept map, may not be viewed in a single outline. Some of the hierarchical relationships among all concepts are lost once several sub-outlines are thus opened, thereby defeating the reason for the outline view.
Third, concept map graphs may have cycles. As a specific example, assume a link connecting nodes A and B with an arrowhead pointing to node B, and a second link pointing from node B to node C, and a third link pointing from node C back to node A. In the INSPIRATION® product's outlines, the link causing the cycle, the link from node C to node A, is ignored. It simply does not appear in the outline. There is no information in the outline portraying the knowledge that C is somehow related to A. In INSPIRATION®, the outline translation of the concept map with the A-to-B-to-C-to-A cycle looks like:
A
A. B                1. CAgain, important semantic information contained in the original graph-based knowledge representation is lost in the translation. The outline does not contain the full complement of knowledge that is in the graph.        
Therefore, a need exists for a system and method that includes, in outline form, all of the semantic and relational information provided in graphical concept maps.